Every winter, drivers are stranded on roads, run the engines of their vehicles until they run out of gas or other vehicle fuel, and then are subjected to hypothermia while they wait for assistance at a location to which they have not brought sufficiently insulating clothing. Skiers or others participating in winter outdoor activities may similarly dress for a planned short time outside, but then fall or otherwise become caught by unexpected conditions that lead to exposure to cold sufficient to produce hypothermia. Still others may find themselves in such conditions with insufficient clothing insulation. Hypothermia is a danger to victims of natural disasters, and even to persons simply changing a tire on a roadside in winter night.
Hypothermia is defined as the unintentional lowering of the deep body (core) temperature below 95.0° F. (35.0° C.). Hypothermia can be mild, moderate, or severe. According to the CDC, 10,649 deaths were attributed to weather-related causes in the United States during the period from 2006 through 2010. Two-thirds of these deaths were attributed to excessive natural cold. (See: Deaths Attributed to Heat, Cold, and Other Weather Events in the United States, 2006-2010; http://www.cdc.gov/nchs/data/nhsr/nhsr076.pdf).
Since 1999, the CDC's National Center for Health Statistics (NCHS) has used information from death certificates categorized with International Classification of Diseases codes to estimate national mortality trends. During 1999, exposure to excessive natural cold (ICD-10 code X31) was listed as the underlying cause of death for 598 persons in the United States, and hypothermia (ICD-10 code T68) was listed as a nature of injury in 1,139 deaths. Of the 598 hypothermia-related deaths, 380 (64%) occurred among males, and 359 (60%) of the 597 persons who died of hypothermia and whose age was known were aged >65 years. During 1999, Pennsylvania and New York had the greatest number of hypothermia-related deaths (36 each), and Alaska had the highest death rate (1.9 per 100,000 population), approximately twice that of Montana, which had second-highest rate (0.9).
Hypothermia during cold weather is the result of decreased heat production, increased heat loss, or impaired thermoregulation. Older persons, who have a decreased basal metabolic rate, might be at further risk for hypothermia because of impaired physical exertion, which produces heat to keep the body warm. Inactivity limits heat production through physical exertion, but overexertion can increase evaporation from the respiratory tract and cause fatigue. Shivering also can cause enough lactate generation eventually to produce acidosis and fatigue. Exposure to high winds can further increase heat loss. As body temperature decreases, the hypothalamus fails to compensate body temperature, and the central nervous system follows the progressive systemic depression of metabolism. Finally, metabolic impairment from alcoholism, malnutrition, hypothyroidism, or advanced age can cause poor endurance to cold. Children, who have a much greater surface—are to metabolic mass, are at even greater risk from hypothermia.
Hypothermia-related morbidity is not exclusive to cold northern climates. Hypothermia can occur in cold and warm climates alike. In fact, a survey of 12 medical centers found that the greatest number of cases of accidental hypothermia occurred in warmer states. Hypothermia has been reported in tropical countries as well. Persons from regions with warmer winters might be at greater risk from the indirect effects of cold weather than persons from regions with colder and longer winters because of inexperience in dealing with cold temperatures. However, geographic distributions might represent not only seasonal temperature variations but also socioeconomic status (which can limit access to controlled indoor temperature), cultural backgrounds (which can influence behavior toward individual protection from cold as well as outdoor activity), or populations with a higher proportion of elderly persons.
The foregoing indicates that an emergency anti-hypothermia system for such conditions is needed. The present invention provides such a system. It provides a thermally insulating inflatable vest that is sufficiently portable to be carried for emergency use in a pocket, purse, backpack, or other such location on a person, or also in a compartment of a vehicle.
The vest provides thermal insulation by being made with air impervious material that also provides for its inflation. The inflating air also provides insulation. Thermal radiation reflective material on inwardly facing surfaces of the vest, preferably inwardly facing surfaces of outer layers of inflated chambers or cells about the vest, serves to retain body heat. The multiplicity of individual inflatable chambers about the vest reduces convection heat transfer. The vest thus preferably provides thermal insulation by anti-conduction, anti-radiation and anti-convection in a highly portable system.
Various other features and attendant advantages of the present invention will become obvious to the reader and become fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings. It is intended that these objects and advantages are within the scope of the present invention. To the accomplishment of the above and related objects, this invention may be embodied in the form illustrated in the accompanying drawings. Attention being called to the fact, however, that the drawings are illustrative only, and that changes may be made in the specific construction illustrated and described within the scope of this application.